During the process for producing semiconductor devices, such as an LSI and a VLSI, a liquid crystal display panel, and the like, various patterns are formed by irradiation with light via a mask (original plate for exposure). When a foreign particle is attached to the mask during the process, the foreign particle absorbs and/or refracts light. This causes reduction of patterning precision to impair the quality and/or appearance of the obtained device. Typically, a pellicle is attached on the surface of a mask to suppress attachment of foreign particles to the mask.
A pellicle is generally composed of a pellicle membrane capable of transmitting light for patterning, and a pellicle frame supporting the periphery of the pellicle membrane. The pellicle frame is composed of a metal such as an aluminum alloy, and may be subjected to anodizing treatment for surface protection. However, various ions such as sulfate ions are likely to remain in the pellicle frame subjected to anodizing treatment. In such a pellicle frame, the residual ions are outgassed to fog up the pellicle membrane, or react with other ions to cause foreign particles, and thus patterning precision becomes more likely to decrease.
To address the above problems, sealing the anodic oxide film is considered, however, the effect thereof is not satisfactory. Protecting of a frame is proposed by electrodepositing an acrylic resin, fluororesin or the like on the surface of the frame (e.g., PTL 1). Electrodepositing a thermosetting resin on the surface of the frame is also proposed (e.g., PTL 2). Further, electrodepositing an epoxy resin on the surface of the frame is also proposed (e.g., PTL 3).